1. Field of the Invention
The present invention relates to an apparatus and a method for generating manuscripts to reproduce a color print, and in particular, to an apparatus and a method for generating by use of a thermal ink sheet four sheets of manuscripts for the toners of complementary colors of three primary colors (i.e. three primary colors of the subtractive mixture of color stimuli) and for the toner of black.
The manuscripts to reproduce the color print generated according to the present invention can be used, for example, in a commonly-used monochrome copying machine to obtain a color copy in which a set of a manuscript and a developing unit having a toner of a color that to the color of the manuscript is sequentially changed so that a toner of a different color is sequentially applied onto the same copy sheet.
2. Description of the Prior Art
Conventionally, the light reflected from a color, original image (an original manuscript) is separated into three primary colors (reference stimuli: blue, green, and red, in general), the sheets of manuscript for printing the separated image in the complementary colors of the three primary colors (the three primary colors of the subtractive mixture of color stimuli: yellow, magenta, and cyan, in general) and a sheet of manuscript for the black printing when required are generated according to the respective separated colors (i.e. images of separated colors), and by using the three or four kinds of manuscripts thus generated, the toner of yellow, magenta, cyan, and black, if required, is sequentially changed to be applied onto the same copy sheet, thereby reproducing the color print.
Incidentally, in each manuscript described above (for the printing of the separated image with the yellow, magenta, cyan, or black toner), the half tone may be represented according to the so-called area gradation method in which the area ratios (or the numbers of dots) are defined for each pixel. The area gradation method is also called a dot density modulating method in which a pixel is further divided into subordinate matrices so that the gradation of a pixel corresponds to the number of dots allocated to each element of the matrices.
For generating the manuscript in general, the so-called thermal copy method for copying the ink from an ink sheet onto a copy sheet is adopted.
In the conventional method described above, however, a plurality of ink sheets are required to generate a set of the manuscripts for the yellow, magenta, cyan, and black printing. This is because the same element of the matrices in the ink sheet can be used only once due to the characteristic of the ink sheet.
Consequently, if the total of area ratios of yellow, magenta, cyan, and black areas exceed 100% for a pixel (or the total dot count of the yellow, magenta, cyan, and black dots exceeds the maximum allowable dot count for the pixel (number of matrix elements)) and hence a color overlap such as between yellow and magenta, magenta and cyan, or cyan and yellow takes place in a region (matrix element) in the pixel, the next copy (generation of the manuscript) cannot be accomplished by use of the same ink sheet in the region where the overlap takes place, and hence the ink sheet must be changed. Such an overlap condition occurs quite frequently.